Understanding Weight Loss Injections – A GP’s Perspective

Author: Dr Aifric Boylan
Read Time: 7-8 minutes

By now, most people have heard about weight loss injections, or have a friend or a family member who is trying them out. And while healthy eating and exercise are still key health goals for most adults, it’s natural to wonder if these medications are worth considering if you are not making progress with your weight management. In this article, we explore the current evidence about weight loss injections in Australia, including how they work, potential side effects, long-term outcomes, who can access them and more.

What Are Weight Loss Injections?

Weight loss injections are prescription medications that help regulate appetite and metabolism- often used when diet and exercise aren’t working. The most common options mimic a “glucagon-like peptide-1 hormone” that is naturally released in your body to reduce hunger. These medications work in a few ways: by slowing down the emptying of food from the stomach, enhancing “satiety” (your sense of fullness after eating), and improving blood sugar control.

In general, they are best viewed as a tool to be used alongside lifestyle changes, including healthy eating and exercise. But they’re not suitable for everyone- so understanding the pros and cons is key to deciding if they’re right for you.

The Evidence: what the research says

Clinical research (such as the STEP1 and SCALE trials) has shown that people using these medications can lose 5-15% body weight loss over 12-18 months. There are slight differences in results between the various available medications. It is important to note that some people do not respond as strongly to treatment.

And the long term results? These injections can maintain weight loss if continued, but it is important to be aware that data beyond 2-3 years is still emerging. Some studies (such as the STEP4 trial in 2021) have shown that patients regain a substantial amount of the lost weight after stopping (though lifestyle factors obviously play a significant part in this too).

Side effects of weight loss injections

There are a few common side effects, though many of the following settle over time, as the body gets used to the medication:

Nausea- feeling queasy, especially when starting/increasing the dose (affects ~20-40% of users).

Vomiting- this may occur alongside nausea, but is typically mild (10-15%).

Diarrhoea- loose stools, which is often temporary as your body adjusts (15-20%).

Indigestion – Heartburn or bloating, linked to slowed digestion (10-12%).

Constipation - some people experience the opposite issue to diarrhoea (10-15%).

Abdominal Pain- mild stomach discomfort or cramps (10-15%).

Reduced Appetite- whilst this is the desired effect, it can feel unpleasant or intense (10-20%).

Tiredness- feeling fatigued, possibly due to appetite changes or side effects (10-15%).

Headaches- Mild to moderate head pain, often early in the treatment program (10-12%).

Lightheadedness - this may be an issue, especially if dehydrated from other side effects (10-12%).

Severe side effects of weight loss injections: severe side effects are rare (affecting less than 1% of users) but can include pancreatitis or gallbladder problems. They may be more likely to occur in people who have high alcohol intake or who have a history of gallbladder issues. Contact your doctor immediately if you experience severe abdominal pain, persistent vomiting, or jaundice.

Do you lose muscle mass when you take weight loss injections?

Some research has shown that people may lose muscle mass, and not just fat when taking weight loss injections. This may account for up to 40% of the weight lost for some individuals! This is obviously a bad outcome- particularly in perimenopausal women who are already prone to losing muscle mass.

That’s why doctors recommend their patients to start an exercise program to build muscle, as well as ensuring adequate protein intake in their diet.

How much exercise?

150 minutes of moderate exercise weekly is a good guideline to start with. It can be helpful to consult a personal trainer, exercise physiologist, physiotherapist to provide some proper structure for you.

How much protein?

Daily dietary protein recommendations vary, but guidelines suggest 1.2-2.0 g/kg body weight daily. This can get a bit tricky to work out by yourself, so it is highly recommended to see a dietitian at least once, to figure out your individual requirements.

Cost and Access in Australia

Expense is also a major consideration, as these injections are not PBS-subsidised for weight loss, and typically cost $150-$500 per month out of pocket, depending on the specific medication and dose. Certain medication brands are slightly cheaper than others, and sometimes the way the medication is prescribed can help with managing the cost (speak to your doctor or pharmacist about this).

Who can get a prescription?

In Australia, AHPRA-registered doctors can prescribe weight loss injections after a thorough assessment. You may be eligible if:

Your BMI is >30, or 27-30 with weight-related conditions (e.g., hypertension, sleep apnea, PCOS, fatty liver, osteoarthritis).
And you’ve tried lifestyle changes without sufficient results.

Weight loss injections generally aren’t suitable if you have a history of medullary thyroid cancer, multiple endocrine neoplasia syndrome (or a family history of these conditions), or severe allergies to the drug. Pregnant or breastfeeding women should avoid them too. Other medical conditions that may rule them out include: a history of severe stomach or gut disorders, gastroparesis, significant liver or kidney disease, eating disorders, pancreatitis or diabetic retinopathy.

What about compounded medications for weight loss?

Supplying compounded medicine without a prescription is illegal - these medicines may be fake and/or pose a significant risk to your health. Speak to your doctor and your pharmacist to ensure you are receiving appropriate, safely produced medication.

What to expect

If prescribed a weight loss injection, you’ll usually start with a low dose, gradually increasing to minimise side effects. Weight loss typically happens within 3-6 months, and lifestyle changes support lasting success.

Ongoing monitoring requirements

As with any medications, the ongoing use of weight loss injections requires ongoing medical supervision- which can be via telehealth or in person. This allows your progress to be monitored, as well as troubleshooting side effects and adjusting the dose if needed. Blood tests may be required from time to time.

If you are having trouble maintaining good habits in the longer term, or you have a bad relationship with food, it is worth considering some sessions with a psychologist to help support you in achieving your health goals.

Conclusion

Weight loss injections can be a very helpful option, as part of a broader approach to well-being, nutrition and fitness. Whilst many people may suffer mild side effects at first, these often settle over time. Long term results and side effects are still not clear. Speak with your GP or one of the doctors on the "Doctors for Weight Loss" team to explore if they’re right for you. We’re here to support your journey with care and evidence-based advice- book your telehealth consult today.

Article references